1. Field of the Invention
The invention relates to the formation of a high resistance resistor for electrostatic discharge protection of insulated gate field effect transistors and more specifically to the formation of a high resistance contacts to the source or drain regions of insulated gate field effect transistors using self aligned silicide contacts.
2. Description of the Related Art
One important method of protection from damage due to electrostatic discharge, or ESD, in insulated gate field effect transistors is to use high resistance resistors to prevent high currents due to ESD. The formation of these high resistance resistors requires a high resistance contact to either the source or drain regions of the field effect transistors. There are process problems which must be overcome in the formation of these high resistance contacts when the low resistance contacts are formed using self aligned silicide methods. In the method taught by this invention titanium at the region where the high resistance contact is to be formed is converted to titanium nitride, using nitrogen ion implantation, and will not form titanium silicide during annealing since the free titanium has been consumed.
In the book VLSI TECHNOLOGY--Second Edition, by S. M. Sze, McGraw Hill Book Co., Singapore, 1988, pages 368-369 ion implantation of nitrogen into silicon is described but not ion implantation of nitrogen into titanium.
In the book SILICON PROCESSING FOR THE VLSI ERA, VOL. 1, Lattice Press, Sunset Beach, Calif., 1986, pages 390-391 there is a discussion of the metallurgical reaction to form refractory metal silicides, but not the use of nitrogen ions to form titanium nitride.